// Shorten a long Trystero/Nostr peer id for display.
export const shortId = (id: string): string => id.slice(0, 8)

// Human-readable byte sizes.
export const formatBytes = (n: number): string => {
  if (n < 1024) return `${n} B`
  const units = ['KB', 'MB', 'GB']
  let v = n / 1024
  let i = 0
  while (v >= 1024 && i < units.length - 1) {
    v /= 1024
    i++
  }
  return `${v.toFixed(v < 10 ? 2 : 1)} ${units[i]}`
}

// A short random id for transfers / log keys.
export const uid = (): string => Math.random().toString(36).slice(2, 10)

// SHA-256 of a buffer, hex-encoded. Used to prove that what arrived on the
// other side is byte-for-byte identical to what was sent.
export const sha256Hex = async (
  data: Uint8Array<ArrayBuffer> | ArrayBuffer
): Promise<string> => {
  const digest = await crypto.subtle.digest('SHA-256', data)
  return [...new Uint8Array(digest)]
    .map(b => b.toString(16).padStart(2, '0'))
    .join('')
}

// Generate `size` bytes of random data, to demo sending large binary payloads
// without needing a file. crypto.getRandomValues caps at 65536 bytes per call,
// so we fill in chunks.
export const randomBytes = (size: number): Uint8Array<ArrayBuffer> => {
  const out = new Uint8Array(size)
  const chunk = 65536
  for (let offset = 0; offset < size; offset += chunk) {
    crypto.getRandomValues(out.subarray(offset, Math.min(offset + chunk, size)))
  }
  return out
}